Methods for preparing articles from processable and dimensionally stable elastomer compositions

Abstract

Methods for preparing a shaped rubber article, comprising admixing at least one thermoplastic material and at least one elastomer material to provide a processable and dimensionally stable rubber composition, shaping the composition, and irradiating the composition to form the shaped rubber article. The dimensional stability of the uncured composition may be provided by partial dynamic vulcanization, high performance reinforcing fillers, fractional curing, or combinations thereof. The elastomer material is present in an amount greater than about 65% by weight based on the total weight of the thermoplastic and elastomer materials present in the admixture.

1. A method for preparing a shaped rubber article, comprising
 (a) admixing a thermoplastic material, an elastomer material, and at least two curatives, wherein the elastomer material is present in an amount greater than about 65% by weight based on the total weight of the thermoplastic and elastomer materials; 
 (b) partially dynamically curing the elastomer material, the partial dynamic curing comprising not reacting at least one of the curatives, wherein a processable composition is formed comprising a thermoplastic phase comprising said thermoplastic material dispersed in a continuous elastomer phase comprising said elastomer material, the composition having a green strength sufficient to inhibit substantial creep of the composition; 
 (c) shaping the processable composition; and 
 (d) irradiating the shaped composition, wherein the composition is finally cured. 
 
     
     
       2. The method of  claim 1 , wherein the elastomer material is present in an amount greater than about 80% by weight. 
     
     
       3. The method of  claim 1 , wherein the at least one of said curatives is selected from the group consisting of sulfur, sulfur donors, peroxides, polyols, and combinations thereof. 
     
     
       4. The method of  claim 1 , wherein the processable composition has a Mooney viscosity (ML1+10 @250° F.) from about 5% to about 100% greater than the uncured viscosity of the composition. 
     
     
       5. The method of  claim 4 , wherein the processable composition has a Mooney viscosity (ML1+10 @250° F.) from about 10% to about 50% greater than the uncured viscosity of the composition. 
     
     
       6. The method of  claim 1 , wherein the green strength is sufficient to provide less than about 1% dimensional change after a 24-hour aging cycle at room temperature. 
     
     
       7. The method of  claim 1 , wherein the green strength is sufficient to provide a tensile strength (ASTM D412) greater than about 50% of the tensile strength of the irradiated composition. 
     
     
       8. The method of  claim 1 , wherein the dimensions of the thermoplastic phase are less than 10 μm as measured by atomic force microscopy on cryogenically microtomed cross-sections of the shaped rubber article. 
     
     
       9. A method of  claim 1 , wherein the thermoplastic material comprises a fluoroplastic. 
     
     
       10. The method of  claim 8 , wherein the fluoroplastic is selected from the group consisting of polyvinylidene fluoride (PVDF), ethylene and tetrafluoroethylene copolymer (ETFE), ethylene and chiorotrifluoroethylene copolymer (ECTFE), copolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride (THY), tetrafluoroethylene and hexafluoropropylene copolymer (FEP), tetrafluoroethylene and perfluoromethylvinylether copolymer (MFA), perfluoroalkoxy (PFA), and combinations thereof. 
     
     
       11. The method of  claim 1 , wherein the elastomer material comprises a fluorocarbon elastomer. 
     
     
       12. The method of  claim 11 , wherein the fluorocarbon elastomer is selected from the group consisting of vinylidene fluoride and hexafluoropropylene copolymer (VDF/HFP); vinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene copolymer (VDF/HFP/TFE); vinylidene fluoride, perfluorovinvl ethers, and tetrafluoroethylene copolymer (VDF/PFVE/TFE); tetrafluoroethvlene and propylene copolymer (TFE/Pr); tetrafluoroethylene, propylene, and vinylidene fluoride copolymer (TFE/Pr/VDF); tetrafluoroethylene, ethylene, perfluorovinyl ethers, and vinylidene fluoride copolymer (TFE/Et/PFVE/VDF); tetrafluoroethylene, ethylene, and perfluorovinyl ethers copolymer (TFE/Et/PFVE); tetrafluoroethylene and perfluorovinyl ethers copolymer (TFE/PFVE); and combinations thereof. 
     
     
       13. The method of  claim 11 , wherein the fluorocarbon elastomer is peroxide-curable. 
     
     
       14. The method of  claim 13 , wherein the fluorocarbon elastomer comprises cure site monomer (CSM). 
     
     
       15. The method of  claim 1 , wherein said elastomer material is an elastomer selected from the group consisting of polyacrylic rubber (ACM), ethylene acrylic rubber (AEM), acrylonitrile butadiene rubber (NBR), hydrogenated acrylonitrile butadiene rubber (HNBR), silicone rubber (SI), polyurethane rubber (PU), natural rubber (NR), and styrene butadiene rubber (SBR), polybutadiene rubber (BR), and combinations thereof. 
     
     
       16. The method of  claim 1 , wherein the thermoplastic material is a thermoplastic selected from the group consisting of polyolefins, polyesters, nylons, polycarbonates, styrene-acrylonitrile copolymers, polyethylene terephthalate, polybutylene terephthalate, polyamides, polystyrene, polystyrene derivatives, polyphenylene oxide, polyoxymethylene, fluorine-containing thermoplastics, and combinations thereof. 
     
     
       17. The method of  claim 1 , wherein the elastomer material comprises (i) a first curable elastomer and (ii) a second curable elastomer having a cure chemistry different than the first curable elastomer. 
     
     
       18. The method of  claim 17 , where the partial dynamic curing comprises curing only elastomer (i) or (ii). 
     
     
       19. The method of  claim 18 , wherein the elastomer (i) is a peroxide-curable fluoroelastomer, elastomer (ii) is a bisphenol-curable fluoroelastomer, and the at least two curatives comprises a peroxide curing agent and a polyol curing agent. 
     
     
       20. The method of  claim 19 , wherein the composition further comprises an olefinic co-agent having at least two sites of olefinic unsaturation. 
     
     
       21. The method of  claim 20 , wherein the olefinic co-agent is triallyisocyanurate (TAlC). 
     
     
       22. The method of  claim 19 , wherein the partial dynamic curing comprises reacting the peroxide curing agent with the peroxide-reactive elastomer at a temperature where the polyol curing agent does not react. 
     
     
       23. The method of  claim 1 , wherein the at least two curatives comprises a first curative that reacts to form crosslinks under different conditions than a second curative. 
     
     
       24. The method of  claim 1 , wherein the shaping comprises a method selected from the group consisting of injection molding, compression molding, transfer molding, blow molding, single layer extrusion, multi-layer extrusion, insert molding, and calendering. 
     
     
       25. The method of  claim 1 , wherein the irradiation is sufficient to inter-link the thermoplastic and elastomer materials. 
     
     
       26. The method of  claim 25 , wherein the type of irradiation is selected from the group consisting of ultraviolet irradiation, infrared irradiation, ionization, electron beam irradiation, x-ray irradiation, γ-ray irradiation, plasma irradiation, corona irradiation, and combinations thereof. 
     
     
       27. The method of  claim 26 , wherein the irradiation is electron beam irradiation. 
     
     
       28. The method of  claim 27 , wherein the irradiation dosage is from about 0.1 to about 40 Mrad. 
     
     
       29. The method of  claim 28 , wherein the irradiation dosage is from about 10 Mrad to about 20 Mrad. 
     
     
       30. The method of  claim 29 , wherein the irradiation dosage is about 18 Mrad. 
     
     
       31. The method of  claim 1 , wherein the composition further comprises high performance reinforcing filler. 
     
     
       32. The method of  claim 1 , wherein the shaping comprises shaping in a form selected from the group consisting of an o-ring, a gasket, and a hose.